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Quality Assurance in Fabrication New Build Power Plants
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Copyright © TWI Ltd 2013
Quality Assurance in FabricationNew Build Power Plants
Marcello Consonni
Welding Engineer
TWI
Copyright © TWI Ltd 2013
A Brief Introduction to TWI
Copyright © TWI Ltd 2013
TWI - Dedicated Resource
• Membership based organisation
• £70M ($115M) of R&D in Materials
Joining, Structural Integrity and
NDT undertaken each year
• Over 780 employees
• Eighteen global offices
• More than 700 Members in 3500
locations in 80 countries
Copyright © TWI Ltd 2013
Support for Power Generation
• Specialist repair procedure development • Fabrication/Fabricator audits • Fitness for service audit/review • Fracture Integrity Management/Life assessment • Risk based Asset Management • Materials properties • Structural and process modelling • Advanced NDT and Conventional NDT • Training in welding and inspection • Manufacturing and repair Codes and Standards
Copyright © TWI Ltd 2013
Webinar Agenda
1. The ‘need’ for this webinar
2. Potential site problems
3. Case study: fabrication audit of CCGT power plant
4. Case study: assessment of power plant contractors
5. Q&A 20-25 min
Copyright © TWI Ltd 2013
Why this webinar?
“…welds were not heat-treated…”
“…caused a …-month delay…”
“…considering sacking key contractors…”
“…welds were not qualified…”
Copyright © TWI Ltd 2013
Potential site problems
• Control of consumables (storage, distribution)
• Welding coordination• Welder skills (specific training)• Control of thermal operations (eg PWHT):
– Specification– Monitoring– Records– Checking
Copyright © TWI Ltd 2013
Competence is key
• The performance of high-Cr grades such as ’91’ and ’92’ is linked to one specific microstructural condition
• Constant surveillance (you get what you inspect…)
• Application of codes and standards is not necessarily adequate!
Copyright © TWI Ltd 2013
P 91 HP Pipework
CCGT Plant
Design Code ASME B31.1
HP steam pipe 450mm x 32mm thick
Hardness in HAZ 449Hv in weld 426Hv
Longitudinal seams in alignment
Is this code compliant?
YES!!
Copyright © TWI Ltd 2013
P 91 HP Pipework
CCGT Plant
Design Code ASME B31.1
HP steam pipe - 90° elbow450mm x 36mm thick
Hardness:182 Hv in HAZ
150Hv in parent
Is this code compliant?
YES!!
Copyright © TWI Ltd 2013
Fabrication Audit – CCGT Plant
Copyright © TWI Ltd 2013
Fabrication Audit – CCGT Plant• Owner’s engineer concerns
wrt workmanship – Four heat recovery steam
generators (HRSGs) with supplementary firing• ASME Section I
– High pressure steam pipes and main superheater outlet headers • P91 steel (9Cr 1Mo modified)
– Header stubs • P22 steel (2¼Cr 1Mo)
– Low pressure components – C-Mn steel
Copyright © TWI Ltd 2013
TWI Scope (Phase 1)
• TWI requested to carry out visual examination at site
• Phase 1- 1 week– Inspect accessible pipe and
header welds – Review level of
workmanship and weld quality
– Comment on acceptability of welds to ASME Section I requirements
Copyright © TWI Ltd 2013
Phase 1 - Results of review
Significant defects observed:
• P91 welds in HRSGs did not comply with ASME Section I quality requirements
• Welding documentation incomplete
• LOW HARDNESS P91 (parent material, welds and HAZs)– Improper PWHT or chemical
composition ?
Copyright © TWI Ltd 2013
Phase 1 - Results of review (2)
Copyright © TWI Ltd 2013
Phase 1 - Recommendations
• Full visual and NDE inspection of all four HRSG’s
• Establish the effects of multiple PWHT (time at temperature) on P91 weldments
• Ensure qualified weld repair procedures• Consider removal of defects by
machining/grinding – to eliminate the need for PWHT
• Investigate low hardness values found on the P91 pipework
Copyright © TWI Ltd 2013
Phase 2 - 6 weeks• TWI expert on site • Witness full inspection and NDE
– Hardness, PMI, UT/PA, RT, Boroscope inspection
• Identify defects and review implications
• Advise on/Review repair qualification
• Advise on HT/PWHT• Recommend remedial work and
supervise implementation• Advise additional testing
– Creep testing for high Mn+Ni (>3.0%) welds
• Liaise with operator, designer, manufacturer and Third Party Inspection agency
Copyright © TWI Ltd 2013
Benefits
Owner assured of integrity of plant
– Delay to plant start up schedule avoided– Confidence gained in operability of the plant
• Additional testing during life of plant to generate data on creep life
– Avoided costly outage and repair once in service• Recommended RBI
– Increase inspection frequency especially for higher risk components with fabrication issues
– Increased safety of plant in operation
Copyright © TWI Ltd 2013
Assessment of contractors
Owner of a large power plant hired TWI to assess potential welding contractors:
1. Preparation of a questionnaire to shortlist contractors:• Welding engineer CVs• Sample WPSs• Technical questions on low-alloyed grades
2. Review of quality system and quality procedures
3. Emphasis on welding coordination: interview of nominated welding engineers
Copyright © TWI Ltd 2013
Ensuring Competence
• Covers all Cr-Mo grades, with emphasis on P91 and other CSEFs
• Attended by: welding engineers, plant inspectors, design engineers, consumable manufacturers
• Can be customised for individual companies
Copyright © TWI Ltd 2013
Any (easy) questions?
Contacts:
marcello.consonni@twi.co.uk
(welding, auditing, training)
ian.froment@twi.co.uk
(membership)
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